Corrosion resisting coatings



July 15, 1958 M. sALo ET AL 2,843,503

CORROSION RESISTING commas Filed Jan. 8, 1954 COAT/N6 COMPRISING CELLULOSE A6E7ATE \NWA PRIME R COMPR/Sl/VG CELLULOSE ACETATE BUT YRA TE A/VD Z/NC TE TROX Y CHROMA T E STEEL SURFACE F lg. 2

' CELLULOSE ACETATE BUTYRATE COAT/N6 CONTAIN/N6 ME THYLOL PHENYL ALLYL E THE R PRIMER COMPR/Sl/VG CELLULOSE ACE MT E BU T YRAT E AND Z/NC T E TROX YCHROMA TE STEEL SURFACE MART/N .SIALO United States Patent O CORROSION RESISTING COATINGS Martin Salo and Gerard J. Clarke, Rochester, N. Y., as-

signors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 8, 1954, Serial No. 403,052

7 Claims. (Cl. 117--85) This invention concerns corrosion-resisting coatings for steel, particularly high butyryl cellulose acetate butyrate coatings As steel has become more and more expensive the problem of losses through corrosion has become increasingly important, and various means have been tried to solve this problem. One important method of treating this problem has been cathodic protection wherein an impressed Current is supplied from a rectifier or generator to the steel member in order to decrease the galvanic action which is responsible for corrosion, particularly to protect underground pipe. Another remedy has been metallic coatings applied over iron, for instance, Zinc or tin which play a sacrificial role in protecting the iron. Clad coatings such as stainless steel or nickel bonded to steel have been used but are expensive. In addition,, glass, porcelain, and cement have been used but suffer from defects such as difficulty in handling and susceptibility to shock damage.

Coatings of the film or skin type such as those from paints of different types have been subject to many disadvantages such as lack of adhesion, susceptibility to corrosion through pin holes in the coating, breakdown of the chemical structure of the coating or inability to withstand the effects of temperature changes or moisture as a result of swelling due to water absorption.

We have discovered a coating which incorporates the desirable advantages of low cost, excellent adhesion, and good durability. Moreover, this coating is easy to apply by spray, dipping and roller coating, and can be made to have a high gloss surface of a pleasing ornamental nature. It can be used alone or as part of a coating system.

One object of this invention is to provide a corrosion resisting coating for steel comprising high butyryl cellulose acetate butyrate. Another object of this invention is to provide a paint suitable for coating metallic surfaceshaving excellent adhesion and pleasing ornamental qualities. A further object is to provide a primer for coating iron and steel which will protect the metal against corrosion and serve as a base for cellulose acetate butyrate coatings. Another object is to provide coating systems having a cellulose acetate butyrate base which protects steel against corrosion.

The above objectives are attained by the use of lacquers containing as the coating ingredients from about 40% methylol phenyl allyl ether and 60-95% cellulose acetate butyrate. We have found that this combination with a properly constituted solvent mixture provides a coating for steel which has high resistance against corrosion. In our preferred embodiment we use a high butyryl cellulose acetate butyrate which has an acetyl content of about 13%, butyryl content of about 37%, hydroxyl content of about 2% and intrinsic viscosity in acetone from about 0.5 to 2.0. This cellulose acetate butyrate has good compatibility with the allylated methylol phenol when used with a carefully compounded solvent mixture. For instance, we have found that a mixture such as one with 30% xylene, 25% toluene, 12% butyl 'ice alcohol, 15% isopropyl alcohol, and 18% butyl acetate is satisfactory. We also find that at least 0.3% phosphoric acid based on the solids content must be added for rapid curing of the coating.

Another embodiment of our invention is illustrated by coating systems in which a primer is used comprising cellulose acetate butyrate, a compatible solvent mixture, and zinc tetroxychrornate. The cellulose acetate butyrate allylated methylol phenol coating may then be applied directly upon the primer followed by a top coat or series of top coats if desired.

In the diagrammatic illustration of our invention, Figures 1 and 2 are longitudinal sectional views through a lacquered coating on a steel surface.

In Figures 1 and 2, a steel surface 1 carries a primer 2 comprising cellulose acetate butyrate and zinc tetroxychromate. Over this primer coating 2 is placed a cellulose acetate butyrate coating 3 containing methylol phenyl allyl ether. A third coating 4, as illustrated in Figure 1, may be added, comprising cellulose acetate butyrate.

The following tables illustrate the preferred embodiment of our invention but are not meant to be limiting in nature.

TABLE I Cellulose acetate butyrate compositions in corrosionproofing of steel i toluene, 10% methyl Gellosolve, 20% #1 ethyl alcohol. b xylene, 25% toluene, 12% butyl alcohol, 15% isopropyl alcohol, 18% butyl acetate.

All coatings were baked 1 /2 hours at 150 C. after the last coat.

TABLE II Corrosion results Composition of Coating Days to Show Corrosion on Steel System (Refer to Table I) Submerged in Tap Water, Room Temp.

Primer Inter- Top mediate Goat A. No corrosion days. 1 3 B. No corrosion 120 days 3 2 O. No corrosion 120 day 3 D. Corrosion 1 day 2 Allylated methylol phenol may be represented by the formula as follows:

in which n may be a number from 1 to 5. These methylol phenyl allyl ethers may be mixtures of two or more of the above isomers in which It varies from 1-5.

We claim:

1. A corrosion-resisting paint comprising 540% methylol phenyl allyl ether, 60-95% cellulose acetate butyrate, solids basis, and a solvent mixture consisting of toluene, xylene, butyl alcohol, isopropyl alcohol and butyl acetate.

2. A corrosion-resisting composition for steel, comprising 40% methylol phenyl allyl ether, 60-95% cellulbse acetate butyrate, about 0.3% phosphoric acid, solids basis,.and a solvent mixture consisting of toluene, xylene, butyl alcohol, isopropyl alcohol and butyl acetate.

3'. An article comprising a steel structure having a coatingcomprising 60-95% cellulose acetate butyrate and 540% methylol phenyl allyl ether coated over a primer comprising about 50% cellulose acetate butyrate and about 50% zinc tetroxychromate.

4'. A process for providing a coat for steel comprising coating the steel With a primer containing about 9% by Weight'cellulose acetate butyrate, 8.6% by Weight zinc tetroxychroma'te and 1.4% talc, and a solvent mixture consisting of toluene, methyl Cellosolve and ethyl alcohol, followed by coating With a composition comprising 60- 95% celluloseacetate butyrate, 5-40% methylol phenyl allyl ether, about 0.3% phosphoric acid, solids basis, and a solvent mixture consisting of xylene, toluene, butyl alcohol, isopropyl alcohol and butyl acetate.

5. An article comprising a steel structure having thereon two successive coatings, the first coating comprising i 50% cellulose acetate butyrate and about 50% zinc tetro'xychromate, the second comprising 6095% cellulose acetate butyrate, 540% methylol phenyl allyl ether and about 0.3% phosphoric acid.

6. A process for providing a corrosion-resisting coating for steel in which at least three successive coatings are applied comprising coating with a primer comprising about 9% cellulose acetate butyrate, 8.6% zinc tetroxychromate, and a solvent mixture consisting of toluene, methyl Cellosolve and ethyl alcohol, applying a second coating comprising 60-95% cellulose acetate butyrate, 540% methylol phenyl allyl ether, about 0.3% phosphoric acid, solids basis, and a solvent mixture consisting of xylene, toluene, butyl alcohol, isopropyl alcohol and butyl acetate, and a third coating comprising 9.1% cellulose acetate butyrate and a solvent mixture consising of Xylene, toluene, butyl alcohol, isopropyl alcohol and butyl acetate.

7. An article comprising a steel structure having thereon a coating comprising a primer containing about cellulose acetate butyrate and 50% zinc tetroxychromate, a second coating comprising 95% cellulose acetate butyrate and 540% methylol phenyl allyl ether, and a third coating substantially consisting of cellulose acetate butyrate.

References Cited in the file of this patent UNITED STATES PATENTS 1,811,040 COX June 23, 1931 2,060,572 Heck Nov. 10, 1936 2,186,454 Gloor Jan. 9, 1940 2,295,814 Wagerle Sept. 15, 1942 2,296,070 Thompson et al- Sept. 15, 1942 2,315,974- Malm et al. Apr. 6, 1943 2,558,243 Gibbon June 26, 1951 2,579,329 Martin Dec. 18, 1951 2,787,557 Christensen Apr. 2, 1957 

6. A PROCESS FOR PROVIDING A CORROSION-RESISTING COATING FOR STEEL IN WHICH AT LEAST THREE SUCCESSIVE COATINGS ARE APPLIED COMPRISING COATING WITHA PRIMER COMPRISING ABOUT 9% CELLULOSE ACETATE BUTYRATE, 8.6% ZINC TETROXYCHROMATE, AND A SOLVENT MIXTURE CONSISTING OF TOLUENE, METHYL CELLOSOLVE AND ETHYL ALOCHOL, APPLYING A SECOND COATING COMPRISING 60-95% CELLULOSE ACETATE BUTYRATE, 5-40% METHYLOL PHENYL ALLYL ETHER, ABOUT 0.3% PHOSPHORIC ACID, SOLIDS BASIS, AND A SOLVENT MIXUTRE CONSISTING OF XYLENE, TOLUENE, BUTYL ALCOHOL, ISOPROPYL ALCOHOL AND BUTYL ACETATE, AND A THIRD COATING COMPRISING 9.1% CELLULOSE ACETATE BUTYRATE AND A SOLVENT MIXTURE CONSISTING OF XYLENE, TOLUENE, BUTYL ALCOHOL, ISOPROPYL ALCOHOL AND BUTYL ACETATE. 